Investigation Into Surface Potential Decay of Polyimide by Unipolar Charge Transport Model

Abstract

To predict spacecraft charging levels and mitigate electrostatic discharges, it is very important to understand the charge transport properties of highly insulating materials such as polyimide. The combination of surface potential decay (SPD) experiment and unipolar charge transport (UCT) model investigates the charge transport properties of polymide. In a simulated space environment chamber, the SPD experiments are performed on polymide. After irradiated by electron beams, the surface potential distributions of the sample are measured by a noncontact potential probe (Trek). The UCT model that consists of relaxation polarization, charge injection, charge migration, charge trapping, and detrapping processes simulates the SPD results. In the numerical UCT model, we solve the charge continuity equation by Runge-Kutta discontinuous Galerkin method and Poisson's equation by boundary element method. The least square error between the experimental and the simulated SPD results is searched by genetic algorithm (GA). From the GA calculation, we optimize the charge transport parameters of polyimide. Then, we calculate the space charge evolution properties during the SPD process of polyimide by the UCT model. These charge transport parameters, then, can be used to study the surface charging or deep dielectric charging of the insulator.Index Terms-Charge transport properties, polyimide, surface potential decay (SPD), unipolar charge transport (UCT).

Charge transport in low density polyethylene based micro/nano-composite with improved thermal conductivity

“…From the viewpoint of energy level, these traps are in the band gap, where an electron trap is between the Fermi level and the bottom of conduction band while a hole trap is between the Fermi level and the top of valence band [28,29]. Taking the electron trap as an example, the trap located close to the bottom of conduction band is usually identified as shallow trap as electrons captured by such traps need lower energy to escape.…”

Dynamic conductivity of polymer dielectrics under time-varying temperature field

“…where E t is the depth in energy of the trap, k B Boltzmann's constant, and T temperature. We use the first-order kinetic charge trapping/detrapping model to express the kinetic process of trapping and detrapping in the form [20][21][22] = - The first term represents the trapping process. The physics mean of (1−q trap /q e N t ) is the capture cross-section.…”

Characteristics of charge and discharge of PMMA samples due to electron irradiation

“…Theoretical studies have simulated the charge process to obtain transient surface potential using radiation-induced conductivity (RIC) method with ignoring effects of SE emissions due to PE scattering and dynamic charging in the sample. [17][18][19][20] Combining with Geant4 used in electron scattering, the RIC method is still appropriate on charge up effects in the space environment of high-energy (MeV) e-beam irradiation. [21] Some other works simulating PE scattering in insulator films with Monte Carlo (MC) method present the dynamic charging effect on SE emission during the charge process, [22,23] showing the influence of SE emission on charge.…”